OS_UpCall 7 (changes)
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OS SWI Calls
» OS_UpCall
» OS_UpCall 7
OS_UpCall 7
(SWI &33)
| Entry | |
|---|---|
| R0 | 7 |
| R1 | Pointer to poll word (in a global memory area, |
| Exit | |
|---|---|
| R0 | Preserved (if V flag clear) |
| Pointer to error block (if V flag set) |
Use
The purpose of this call is to call inform the TaskWindow module that an open pipe has been closed or deleted
Notes
It is made by PipeFS if an open pipe is closed or deleted. It’s not available in RISC OS 2.
The Task Window module then traps this and objects if any of its tasks are currently waiting for the poll word related to that pipe to become non non-zero, zero, by returning an error.
This prevents a *Shut command from deleting the workspace which is being accessed by the Task Window, which could potentially cause address exceptions.
See also
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